1. Field of the Invention
The present invention relates to an image signal processing apparatus applied to a surveillance camera system, for example. More specifically, the present invention relates to an image signal processing apparatus for performing in parallel individual compression of a plurality of image signals and individual expansion of a plurality of compressed image signals.
2. Description of the Prior Art
In conventional such a kind of image signal processing apparatus, when recording is instructed, image signals sequentially fetched from a surveillance camera are individually compressed by a JPEG format and then, compressed image signals are recorded onto a recording medium. Furthermore, when reproducing is instructed, the compressed image signals sequentially read from the recording medium are individually expanded by the JPEG format so as to output expanded image signals on a monitor.
However, a conventional recording medium is a tape medium such as a video tape and is not designated on the assumption that a recording instruction and a reproducing instruction are simultaneously applied and therefore, compression processing and expansion processing are never simultaneously executed. On the other hand, recently, a disk medium such as a hard disk comes into wide use as a recording medium so as to desire parallel processing between compression and expansion. Herein, a frame lacking occurring to reproduced expanded signals due to delay of processing becomes insignificant while a frame lacking occurring to recorded compressed image signals should be avoided for the sake of a recording property.